C# Class having different set of operations applied to

Question

I have a class with some properties, eg

public class Foo {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }
}

Now I want to have copy of Foo, while applying some operations on certain properties.

I could do a new method like so:

public static Foo ReplaceSomethingInFoo(Foo foo) {
    var newFoo = ...;
    newFoo.Prop1 = foo.Prop1.Replace(....);
    return newFoo;
}

If I need another view of Foo, I create yet another method.

Is there a more reuseable way of doing that?

I was thinking about having an attribute to those properties which define those views. Maybe something like this:

public class Foo {
    [ViewMode(Mode="Name1", ViewClass=ViewClassWithOperations)
    public string Prop1 { get; set; }
}

Where ViewClassWithOperations are the operations applied to the properties. And with the Mode-Name I could decide which ViewClass I should instantiate and apply to Foo.

Does this even make sense? Is it too complicated? Do you have better ideas?

Answer 1

Take a look at C# Record Types (coming soon to C#). They include a With method that behaves like this:

 public Foo With(string prop1 = this.Prop1, string prop2 = this.prop2) 
    => new Foo(prop1, prop2);

You can implement that today in C# and then call it passing named arguments for the properties you want to replace.

But when you say 'View' it sounds like you maybe should consider implementing a separate ViewModel class for Foo and maybe using Automapper to map properties across because sooner or later you will need a view like 'name' which is maybe constructed from 'first name + space + last name'. Reusing domain models as view models typically leads to problems down the line.